The present invention relates to a fastener. In particular, the invention relates to a screw nut, by means of which the torque or the clamping force that is produced by screwing a screw onto a component to be fastened is limited. Furthermore, the invention relates to the use of such a screw nut according to the invention in a retainer module for affixing lines so that the clamping forces for affixing that can be applied to the lines can be limited in a defined manner.
As a rule, screw-to-nut connections are used in order to subject components that are located between the screw head and the screw nut to clamping force so that the position of these components is fixed. Often there is a requirement for limiting the clamping force that can be produced by way of the screw and the nut, either so as not to exceed the permissible tensile stress in the shaft of the screw or so as to limit the clamping forces acting on the components, in view of the permissible material stress of the components. Since, as a rule, there is a linear connection between these clamping forces and torques that are applied to the screw-to-nut connection, normally the torque is used as a guide value by means of which conclusions can be drawn in relation to the clamping force produced.
In order to be able to exert a defined clamping force onto a screw-to-nut connection, frequently so-called torque wrenches are used, by means of which a predeterminable torque, and thus a certain clamping force, can be applied to the screw-to-nut connection. Such torque wrenches frequently have a very expensive adjustment mechanism by means of which the torque that can be produced with the torque wrench can be set, wherein exceeding the torque causes the torque wrench either to generate an audible noise or to automatically disengage, i.e. rotate without load. While with the use of such torque wrenches a predeterminable torque can be applied to a screw-to-nut connection, such torque wrenches are however, as a rule, very large, heavy and therefore also relatively unwieldy to use so that they are in many respects associated with disadvantages.
In particular if thousands of screw-to-nut connections are to be tightened with such a torque wrench, as is, for example, the case when assembling aircraft structures, the handling of such large and heavy torque wrenches is unsatisfactory from an ergonomic point of view. Furthermore, in particular in the field of assembling aircraft structures, the screw-to-nut connections are frequently difficult to access so that with the use of such a large torque wrench they are either inaccessible or barely accessible.